"She declared this was the worst pain she ever had, many times worse than childbirth," the doctor said. "This is not something that she had any doubts there was a problem with."

After examining her and doing some diagnostic tests, doctors determined Bush had a perforated ulcer in her duodenum, the first portion of the small intestine after the stomach, Reardon said.

In the operating room, doctors thoroughly cleaned her abdominal cavity of any contaminants that had leaked through the hole, described by the hospital as being 1 centimeter. Then, doctors repaired the ulcer and used a piece of the omentum, living fat tissue in the abdomen, to sew on top of it to seal it, Reardon said.

Bush remained in the hospital's intensive care unit Wednesday, standard procedure following such surgery.

She likely will be there at least 24 to 48 hours, he said. She likely will be hospitalized for at least a week, Reardon said, and won't be able to have any food by mouth, as it might stretch the newly repaired ulcer.

She also requires intravenous antibiotics to counteract any bacteria released into the abdomen through the hole.

"She's awake and completely alert," he said. "She's been visiting with the family and looks very good."

The condition was caught early, as Bush recognized there was something wrong, Reardon said. He suggested anti-inflammatory medication Bush takes may have caused the ulcer -- a rare but not unheard-of complication.

"It's uncommon, but it's not so uncommon that we don't know how to treat it," he said.

The ulcer was biopsied and is benign, he said. "If there were any concerns, the operation would have been a different operation."

Former President George H.W. Bush was with his wife, Reardon said. "They're very affectionate to each other. I hope my marriage is that good, that far into it. He's got a very positive attitude."

The mother of President George W. Bush, Barbara Bush was first lady from 1989 to 1993.

Born Barbara Pierce in New York in 1925, she married her husband in 1945. She is a distant cousin of Franklin Pierce, who served as president from 1853 to 1857.

She and the former president split their time between Houston and Kennebunkport, Maine.